Geometrically distorted luminance in a multi-lens camera

ABSTRACT

Spatial resolution can be improved in multi-lens digital cameras. Each lens can have the same or similar field of view, but can be associated with different geometric distortions defining, for example, a magnification at various field of view portions. A final image can be generated based on an initial image captured by each lens. Luminance information from the magnified portions of the initial images can be combined to form final image luminance information. Chrominance information from the initial images can be combined to form final image chrominance information. The final image can be generated based on the final image luminance information and the final image chrominance information.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase application of PCT/NL2011/050723,entitled “System and Method for Imaging Using Multi Aperture Camera,”filed on Oct. 24, 2011, which in turn claims priority to U.S.Provisional Application No. 61/406,148, filed on Oct. 24, 2010, thecontents of which are all hereby incorporated by reference in theirentirety.

BACKGROUND

1. Technical Field

This disclosure relates to a camera system, and more specifically, to acamera system with multiple lenses, each configured to capturegeometrically-distorted image data of a portion of a field of view foruse in generating images.

2. Description of the Related Art

An imaging system typically consists of an imaging lens and an imagesensor. An imaging lens collects light emitted or reflected from objectsin a scene and directs collected light upon the image sensor. An imagesensor is a photosensitive device that converts light incident upon theimage sensor during an image capture to an electronic signalrepresentative of the captured light. To obtain color image data, acolor filter array (such as a Bayer filter) is used in conjunction withthe image sensor to separate between different spectral regions of thetotal light spectrum of the image being captured. Color filter arraysseparate captured light into (for instance) green image planes, redimage planes, and blue image planes.

Given an image sensor's active area dimension (the image sensor's“format”) and the desired field of view, the focal length of a lens canbe calculated. The size of the aperture of the lens can be set accordingto image sensor's photo sensitivity, exposure time, and noise leveltolerance. The focal length divided by the aperture's size is called the“F-number,” and indicates the ability of the lens to collect light.Lower F-Numbers are associated with more light being collected by thelens and directed upon the image sensor.

A phenomena caused by the use of color filter arrays is the appearanceof color artifacts also caused by the spatial disposition of thedifferent colors. For example, in a captured image of a white line 1pixel deep on a black background, the white line will appear in variouscolors depending on the position of the light from the line incidentupon the image sensor. Multi-lens systems can be implemented to reducesuch artifacts, but can be accompanied by issues of increased systemcost and complexity.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed embodiments have other advantages and features which willbe more readily apparent from the following detailed description of theinvention and the appended claims, when taken in conjunction with theaccompanying drawings, in which:

FIG. (or “FIG.”) 1 illustrates a side view of a single lens camera,according to one example embodiment.

FIG. 2 illustrates a color filter array having multiple pixels,according to one example embodiment.

FIG. 3 illustrates a side view of a three lens camera having one imagesensor and three lenses, according to one example embodiment.

FIG. 4 illustrates an example of a scene as projected on to an imagesensor, according to one example embodiment.

FIG. 5 illustrates a front view of a three lens camera using onerectangular image sensor divided in to three regions, according to oneexample embodiment.

FIG. 6 illustrates a front view of a three lens camera having one imagesensor, one large lens and two smaller lenses, according to one exampleembodiment.

FIG. 7 illustrates a front view of a four lens camera having a one imagesensor and four lenses, according to one example embodiment.

FIG. 8 illustrates a 16 lens camera having four regions, each containingfour lenses as illustrated in FIG. 7, according to one exampleembodiment.

FIG. 9 illustrates the focal length variation as a function of field ofview for a three lens camera system, according to one exampleembodiment.

FIG. 10 illustrates the focal length variation as a function of field ofview for a two lens camera system, according to one example embodiment.

FIG. 11 illustrates an embodiment of a section of a multi-lens digitalcamera, according to one example embodiment.

FIG. 12 illustrates an exploded view of the individual camera componentsshown in FIG. 11, according to one example embodiment.

FIG. 13A illustrates individual lens elements in a 2×2 lens array,according to one example embodiment.

FIG. 13B illustrates a top view of the 2×2 lens array shown in FIG. 13A,according to one example embodiment.

FIG. 14A illustrates one lens element in a 2×2 lens array integratedlens element, according to one example embodiment.

FIG. 14B illustrates a top view of the integrated 2×2 lens array shownin FIG. 14A, according to one example embodiment.

FIGS. 15A, 16A, 17A, 18, and 19 illustrate various multi-lens arrays,according to one example embodiment.

FIGS. 15B, 16B, and 17B illustrate image sensors for use with themulti-lens arrays of FIGS. 15A, 16A, and 17A, respectively, according toone example embodiment.

FIGS. 20, 21, 22, and 23 illustrate multi-lens camera components,according to one example embodiment.

DETAILED DESCRIPTION

The figures and the following description relate to preferredembodiments by way of illustration only. It should be noted that fromthe following discussion, alternative embodiments of the structures andmethods disclosed herein will be readily recognized as viablealternatives that may be employed without departing from the principlesof what is claimed.

Reference will now be made in detail to several embodiments, examples ofwhich are illustrated in the accompanying figures. It is noted thatwherever practicable similar or like reference numbers may be used inthe figures and may indicate similar or like functionality. The figuresdepict embodiments of the disclosed system (or method) for purposes ofillustration only. One skilled in the art will readily recognize fromthe following description that alternative embodiments of the structuresand methods illustrated herein may be employed without departing fromthe principles described herein.

A multi-lens camera system can improve image luminance by, for eachlens, magnifying light collected from a portion of a field of view anddirected onto an image sensor. The lens can magnify light collectionfrom a portion of the field of view based on a geometric distortion thatdefines a light magnification or focal length variation by field of viewportion or location. The image sensor captures an image from each lens,and combines the luminance information resulting from the magnifiedportions of the field of view to produce combined luminance informationfor a final image. Each lens in such a camera system is associated witha different portion of a field of view, and each portion of the field ofview is represented by at least one lens. The term “multi-lens digitalcamera” or “multi-aperture digital camera” as used herein refers to acamera including more than one lens, each with an aperture and variouslens elements. Thus, instead of using a single lens to capture luminanceinformation for a field of view, several smaller lenses can be used,each capturing a magnified portion of the field of view.

Geometrically Distorted Luminance Overview

The multi-lens camera system described herein can overcome the loss ofeffective resolution originating from the use of multiple lowerresolution lenses (as opposed to one higher resolution lens). Themulti-lens camera system can improve image spatial resolution using amulti lens digital camera, each lens having a different geometricdistortion as a function of field of view. Each lens in the multi-lenscamera system forms an initial image at a different location on theimage sensor, and each initial image includes a magnified portion of afield of view. The image sensor then combines the initial image to forma final image.

In one embodiment, each lens is associated with a different geometricdistortion as a function of field of view, and is configured to magnifydifferent parts of the image based on the geometric distortion. Ageometric distortion associated with a lens is preferably achieved byvarious optical properties of the lens, such as the lens shape, the lensthickness, the air space thickness, the lens materials, and the lensaperture dimensions.

The multi-lens camera system can include one or more color filters,polarized filters, chromatic filters, and neutral density filtersintegrated within the system configured to filter collected light priorto capture by the image sensor. Each initial image can have a differentlight intensity from other initial images. The camera system can includean algorithm for adding initial images to form a final image havinghigher dynamic range than the initial images. Each lens in themulti-lens camera system can have a different F-Number than the otherlenses, and can be focused to a different distance than the otherlenses.

In one embodiment, the multi-lens camera system described herein isconfigured to: 1. select a magnified portion of each initial imageassociated with a portion of a field of view, 2. correct the magnifiedportions of the initial images, and 3. combine the corrected portions ofthe initial images to form a final image. The final image can have ahigher resolution than any of the initial images, thus allowing lowerresolution lenses to produce an image of similar quality to a higherresolution lens.

In one embodiment, the multi-lens camera system described herein isconfigured to: 1. correct the magnified portions of the initial images,2. select an area of interest one or more of the corrected imagescorresponding to the magnified portions of the initial images, 3.combine the initial image luminance information of the selected areas ofinterest to form final image luminance information, 4. combine theinitial image chrominance information to form final image chrominanceinformation, and 5. combining the final image luminance information andthe final image chrominance information to form a final image.

Each magnified portion of an initial image can be of a higher resolutionthan the remainder of the initial image. The final image luminanceinformation can be a luminance matrix including the luminanceinformation of each selected area of interest of the corrected images.The final image chrominance information can be a chrominance matrixincluding the chrominance information of each corrected image.Accordingly, the final image can be created by combining the luminancematrix and the chrominance matrix. It should be noted that the methodsdescribed herein can additionally include upscaling the initial images,for instance before or after the magnified portions of the initialimages are corrected.

In one embodiment, the camera system described herein is configuredto: 1. correct the geometric distortion of initial images captured fromone or more lenses, 2. select an area of interest corresponding to ageometrically distorted portion of at least two initial images, 3.create final image luminance information based on the selected areas ofinterest, 4. create final image chrominance information from at leasttwo corrected initial images captured with different chromatic filters,and 5. combine the final image luminance information and the final imagechrominance information to form a final image. This and other methodsdescribed herein can beneficially correct for low light performance ofone or more lens in the camera system. The final image luminanceinformation described herein can have a higher signal to noise ratiothan the initial image luminance information of one or more initialimages.

In one embodiment, the camera system described herein is configuredto: 1. determine an amount of light in a scene, 2. select a source ofluminance for one or more portions of the final image based on thedetermined amount of light, and 3. selecting areas of interest ofinitial images as described herein based on the selected sources ofluminance. Such a method allows for the dynamic selection of the sourceof luminance for a given final image portion, and as such improves thesignal to noise ratio of the final image in low lighting conditions. Theamount of light in a scene can be calculated by using the exposure timeand the pixels signal values associated with one or more initial images.

In one embodiment, the camera system described herein is configuredto: 1. select a portion of a field of view, 2. select a source ofluminance for the selected portion of the field of view from a pluralityof initial images captured by a plurality of lenses, and 3. creatingfinal image luminance information based at least in part on the selectedsource of luminance as described herein. The methods described hereincan result in a higher resolution monochrome image than a monochromeimage captured by an individual lens of the multi-lens camera systemdescribed herein. The source of luminance can be selected between abroader spectrally filtered initial image that may be corrected fordistortion and a chromatically filtered initial image that may becorrected for distortion.

In the multi-lens camera systems described herein, each lens can form aninitial image that is smaller than the size of the one or more imagesensors. The resulting initial images can have a lower effectiveresolution than an image captured by a larger lens with a highereffective resolution.

In the multi-lens camera systems described herein, each lens can includean integrated optical barrier for blocking light. Such barriers can becreated using, for example, a dicing technique, powder blasting,etching, or scoring techniques. Canals can be created lens opticalelements using, for example, dicing techniques. Preferably, the barriersare created within or on top of an image sensor cover substrate.

Optical wafers can have multiple integrated barriers or canals that canbe filled with optical absorbing material. The wafer can have multiplecanals with surfaces that are coated with absorbing coating. It is alsopossible to coat different locations on the wafer surface, the coatingsat each location configured to transmit a different light spectrum,especially where each location on the wafer is associated with thearrangement of sub images.

The multi-lens camera systems described herein can also include two ormore lenses wherein each lens comprises one or more optical elementswhere some or all have a non circular aperture allowing a decrease indistances between the lenses. The largest lens element in each lens hasa footprint which is smaller than the size of the image sensor area thatis used to collect the light passing through the same lens. In additionsome optical elements have a non circular aperture and others have acircular aperture.

The multi-lens camera systems described herein beneficially allow forincreasing the effective resolution of a multi aperture camera withoutthe need of using a sensor with more pixels. The present system thusrelates to the use of a multi aperture digital camera having at leasttwo different transfer functions, as a function of field, of lenses ofthe different imaging channels for improving image spatial resolution.

In one embodiment, the multi-lens camera system relates to the use of amulti aperture digital camera having at least two different transferfunctions, as a function of field, of lenses of the different imagingchannels for improving low light imaging performance.

In an imaging system containing multi apertures as described above, eachlens and the area of the sensor in which the lens forms an image on canbe referred to as an imaging channel. The digital camera is composed oftwo or more imaging channels where the imaging lens of each channel canbe different than the imaging lens of other channels.

The focal length of a lens is defined by the distance in which the lenswill form an image of an object that is positioned at infinity. The lensF-Number is defined as the focal length divided by the entrance pupildiameter which is set by the lens aperture. The maximal achievablemodulation transfer function of a lens with a given F-Number is limitedby the diffraction effect.

An ideal lens can have constant magnification and focal length acrossits field of view, but an actual lens typically demonstrates opticaldistortion (defined as a change of magnification across the field ofview of the lens). For actual lenses with distortion, the focal lengthis typically defined for the center of the field of view, which can bereferred to as ‘on-axis’.

Lenses that are rotational symmetric can demonstrate a distortion graphthat is symmetric around the optical axis of the lens. Positivedistortion at a certain region of the field of view indicates that thefocal length at this region is higher than it is at the center of thefield of view. Respectively, negative distortion at a certain region ofthe field of view indicates that the focal length at the said region isshorter than at the center of the field of view.

Each lens of a multi-lens camera system can include a differentchromatic filter, or no chromatic filter. Each lens can be designed tohave a longer focal length for a portion of the field of view. Using aspecial algorithm for combining the details captured by all or some ofthe lenses and their corresponding distorted portions of the field ofview can result in a digital image of the field of view with highresolution over the field of view.

The multi-lens camera system described herein can produce ahigh-resolution final image that composed by extracting portions ofinitial images corresponding to distorted initial image portions fromdifferent lenses. The final image can be a monochrome image. Convertingthis image into a color image can require the extraction of chrominanceinformation for each pixel or pixel groups from some or all of initialimages.

System Overview

The system and method described herein provide high quality imagingwhile considerably reducing the length of the camera as compared toother systems and methods.

FIG. 1 illustrates a side view of a single lens camera having a singlelens (102) that can include one or more elements and a single sensor(101). FIG. 2 illustrates a sensor array (201) having multiple pixelswhere the position of the green filter, red filter and blue filter aremarked by (202), (203) and (204) respectively. The image that will betaken using this configuration needs to be processed in order toseparate the green, red and blue images.

FIG. 3 illustrates a side view of a three lens camera having one sensor(310) and three lenses (301), (302) and (303). Each one of the said lenswill project the image of the same scene on to segments of the sensormarked by (311), (312), and (313) respectively. Each one of the threelenses will have different color filters integrated within the lens, infront of it or between the lens and sensor (310). Using the describedconfiguration the image acquired by the sensor will be composed of twoor more smaller images, each imaging information from the scene atdifferent spectrums.

FIG. 4 illustrates an example of a scene as projected on to the sensor(401), in each region of the sensor (402), (403) and (404) the samescene is projected but each region will contain information for light atdifferent wavelengths representing different colors according to thefilters integrated within the lens that forms the image on each region.

The described configuration does not require the use of a color filterarray and therefore the maximal spatial frequency that can be resolvedby the sensor can be higher. On the other hand, using smaller lens andsmaller active area per channel can result in a smaller focal length ofthe lens. Therefore, the spatial resolution of objects can be decreased,and the maximal resolvable resolution for each color can remain thesame.

The image acquired by the sensor is composed of two or more smallerimages, each containing information of the same scene but in differentcolors. The complete image is then processed and separated in to 3 ormore smaller images and combined together to one large color image.

The described method of imaging has many advantages:

-   -   1. Shorter lens track (height): Each one of the lenses used can        be smaller in size than the single lens covering the same field        of view. The total track (height) of each lens can be smaller,        allowing the camera to be smaller in height, an important factor        for mobile phone cameras, notebook cameras and other        applications requiring short optical track.    -   2. Reduced Color artifacts: Since each color is captured        separately, artifacts originating from spatial dependency of        each color in a color filter array can be reduced.    -   3. Lens requirements: Each lens does not have to be optimal for        all spectrums used, simplifying the lens design and possibly        decreasing the amount of elements used in each lens as no color        correction may be needed.    -   4. Larger Depth of Focus: The depth of focus of a system depends        on its focal length. Since smaller lenses are used with smaller        focal lengths, the depth of focus is increased by the scale        factor, squared.    -   5. Elimination of focus mechanism: Focus mechanisms can change        the distance between the lens and the sensor to compensate for        the change in object distance and to assure that the desired        distance is in focus during the exposure time. Such a mechanism        can be costly and can have many other disadvantages such as        increased size, increased power consumption, shutter lag,        decreased reliability, and increased price.

Using a fourth lens in addition to the three used for each color red,green and blue (or other colors) with a broad spectral transmission canallow extension of the sensor's dynamic range and can improve thesignal-to-noise performance of the camera in low light conditions.

All configurations described above using a fourth lens element can beapplied to configurations having two or more lenses.

Another configuration uses two or more lenses with one sensor having acolor filter array integrated or on top of the sensor such as a Bayerfilter array. In such a configuration no color filter will be integratedin to each lens channel and all lenses will create a color image on thesensor region corresponding to the specific lens. The resulting imagewill be processed to form one large image combining the two or morecolor images that are projected on to the sensor.

Dividing the sensor's active area in to 3 areas, one for each of red,green, and blue (for example), can be achieved by placing 3 lenses asillustrated in the figures. The resulting image will include 3 smallimages containing information of the same scene in a different color.

FIG. 5 illustrates a front view of a three lens camera using onerectangular sensor (500) divided in to three regions (501), (502) and(503). The three lenses (511), (512) and (513) each having differentcolor filters integrated within the lens, in front of the lens orbetween the lens and the sensor are used to form an image of the samescene but in different colors. In this example each region of the sensor(501), (502) and (503) are rectangular having the longer dimension ofthe rectangle perpendicular to the long dimension of the completesensor.

Other three lens configuration can be used, such as using a larger greenfiltered lens and two smaller lenses for blue and red, such aconfiguration will results in higher spatial resolution in the greenchannel since more pixels are being used.

FIG. 6 illustrates a front view of a three lens camera having one sensor(600), one large lens (613) and two smaller lenses (611) and (612). Thelarge lens (613) is used to form an image on the sensor segment marked(603) while the two smaller lenses form an image on the sensor'ssegments marked with (601) and (602) respectively. The larger lens (613)can use a green color filter while the two smaller lenses (611) and(612) can use a blue and red filter respectively. Other color filterscould be used for each lens.

A four lens camera includes 4 lenses each having a different colorfilter integrated within the lens, in front of the lens, or between thelens and the sensor region corresponding to the lens. The color filterused for two lenses can be the same, resulting in a particular colorfilter appearing twice among the 4 lenses.

FIG. 7 illustrates a front view of a four lens camera having one sensor(700) and four lenses (711), (712),(713) and (714). Each lens forms animage on the corresponding sensor region marked with (701), (702),(703)and (704) respectively. Each one of the lenses will be integrated with acolor filter within the lens, in front of the lens, or between the lensand the sensor. All four lenses can be integrated with different colorfilters, or two of the four lenses can be integrated with the same colorfilter. For example, two green filters, one blue filter, and one redfilter can allow more light collection in the green spectrum.

FIG. 8 illustrates a 16 lens camera having 4 regions (801), (802), (803)and (804), each containing four lenses as illustrated in FIG. 7.

A camera system with 3 imaging channels can have a different colorfilter integrated within each imaging channel, one for each of red,green, and blue. All imaging channels have the same diagonal field ofview. In this embodiment, the lenses of the imaging channels weredesigned to have higher magnification at different areas of the image.The higher magnification is introduced by geometrically distortingportions of the image captured by each lens. FIG. 9 illustrates a graphof focal length in which the magnification of each imaging channels ishigher at a part of the field of view.

The imaging channel (channel 1 in FIG. 9) including a green color filterdemonstrates higher magnification at the center of the field of view,The imaging channel (channel 2 in FIG. 9) including a red color filterdemonstrates higher magnification between the central area of the fieldof view and up to an area close to the corner of the field of view. Theimaging channel (channel 3 in FIG. 9) including a blue color filterdemonstrates higher magnification at the corner of the field of view.

FIG. 9 illustrates the focal length variation as a function of field ofview for the three lenses of the first embodiment. As seen in the graphat any given field of view at least one imaging channel images the scenewith a higher focal (and accordingly, a higher magnification).

After capturing images or during image readout, images captured by eachlens are corrected for distortion and upscaled by a factor greater thanone. A luminance matrix is then created according to one of the twomethods:

-   -   1. At each area of the final image one or more pixels in size,        the source of luminance is chosen from one of the three imaging        channels according to a predefined table that for each area        selects the source of luminance according to the imaging channel        having the highest magnification in the said area, or    -   2. Comparing sharpness of each area or detail in the three        imaging channels and choosing the sharpest one as the source of        luminance.

In both cases a chrominance matrix is also created using thedistortion-corrected and upscaled images of the three imaging channels.

The luminance and chrominance matrix contain sufficient information as acolor image. Converting the luminance and chrominance into other imageformats such as RGB, YUV or any other known format is not described herebut is a well known procedure.

A camera system with 4 imaging channels can have a different colorfilter integrated within each imaging channel, one for each of red,green, blue, and white. The white color filter has a wider spectraltransmission compared to the other colors. All imaging channels have thesame diagonal field of view. In this embodiment, the lenses of theimaging channels that include the red, green, and blue filters weredesigned to have higher magnification at a different area of the image.The higher magnification is introduced by geometrically distortingportions of the image captured by each lens. FIG. 9 illustrates a graphof focal length in which the magnification of each imaging channels ishigher at a part of the field of view. The white channel can have verylittle or no distortion resulting in a uniform magnification as afunction of field of view.

The imaging channel (channel 1 in FIG. 9) including a green color filterdemonstrates higher magnification at the center of the field of view.The imaging channel (channel 2 in FIG. 9) including a red color filterdemonstrates higher magnification between the central area of the fieldof view and the area close to the corners of the field of view. Theimaging channel (channel 3 in FIG. 9) including a blue color filterdemonstrates higher magnification at the corners of the field of view.

FIG. 9 illustrates the focal length variation as a function of field ofview for the three lenses of the first embodiment. As seen in the graphat any given field of view at least one imaging channel images the scenewith a higher focal length (and accordingly, a higher magnification).

After capturing images or during image readout, images captured by eachlens are corrected for distortion and upscaled by a factor of 2. Aluminance matrix is then created according to one of the two methods:

-   -   1. At each area of the final image that can be one or more        pixels in size, the source of luminance is chosen from one of        the three imaging channels according to predefined table that        for each area selects the source of luminance according to the        imaging channel having the highest magnification in the said        area, or    -   2. Comparing the sharpness of each area or detail in the three        imaging channels and choosing the sharpest one as the source of        luminance, or    -   3. Using the image of the imaging channel that includes a white        channel.

A smart algorithm can choose to use one of the above three methods forcomputing the luminance matrix by determining the amount of light in ascene. The amount of light can be estimated by the exposure time and thesignals or average signal in the image of one or more imaging channels.

In case of low lighting conditions it is preferred to use the thirdmethod of creating the luminance matrix using the white channel only asthis channel will demonstrate a higher signal-to-noise ratio which leadsto lower noise in the final image. The decision can be done on a globallevel or on a pixel or area level allowing the use of information fromall four imaging channels for creating the luminance matrix. In thiscase the luminance of bright areas in the scene will be created usingone of the three color channels and luminance at darker areas will becreated using information from the white channel. In both cases achrominance matrix is also created using the distortion-correctedupscaled images of the three imaging channels or using the fourchannels. The luminance and chrominance matrix contain sufficientinformation as a color image.

A camera system with 2 imaging channels can include filters that use thesame spectrum. One of the imaging channels can be designed to havehigher magnification at the central area of the image and the otherimaging channel can be designed to have higher magnification at theperipheral area of the image. The higher magnification is introduced bygeometrically distorting portions of the image captured by each lens.

FIG. 10 illustrates the focal length variation as a function of field ofview for the two lenses of the third embodiment. As seen in FIG. 10, atany given field of view, at least one imaging channel images a scenewith a higher focal length and accordingly, higher magnification.

After capturing the images or during image readout, images captured byeach lens are corrected for distortion and upscaled by a factor greaterthan 1. A combined image is then created according to one of the twomethods:

-   -   1. At each area of the final image that can be one or more        pixels in size, the source image is chosen from one of the two        imaging channels according to predefined table that for each        area selects the source image according to the imaging channel        having the highest magnification in the said area, or    -   2. Comparing sharpness of each area or detail in the two imaging        channels and choosing the sharpest one as the source.

FIG. 11 illustrates an embodiment of a section of multi aperture digitalcamera, i.e. a lens package 1100. The lens package 1100 comprises animage capturing element 1101, e.g. a Charge Coupled imaging Device (CCD)or a CMOS imaging device (the “image sensor” herein). In general such animage capturing element 1101 is referred to as a solid-state imagesensor (SSIS). The image capturing element 1101 converts optical imagesof the subject formed by the lens elements of the lens array 1103 intoan image signal (data). The image capturing element 1101 is mounted on asubstrate (not shown) and comprises a cover 1102 for protecting thesensor against the environment. The lens array 1103 is housed in a lensholder 104, and the lens holder 1104 is provided with a cover plate1105. The lens holder 1104 has the function of a spacer as well, becausethe lens array 1103 is supported by the lens holder 1104. The height ofthis support determines for a dominant part the distance between thelens array 1103 and the sensor 1101. The cover plate may includeoptionally baffle. Light falls into the cover plate 1105 and travelsthrough the lens array 1103 to the sensor 1101. The individual parts maybe bonded by an adhesive layer (not shown). Preferably, the one or moreadhesive layers are rim-shaped, the adhesive material being presentoutside an area coinciding with the projection of the circumference ofthe lens elements present in the lens array.

FIG. 12 illustrates an exploded view of the individual parts shown inFIG. 11.

FIG. 13A illustrates individual lens elements 1106 in a 2×2 array placedon a sensor 1101.

FIG. 13B illustrates a top view of the 2×2 array shown in FIG. 13A.

FIG. 14A illustrates one lens element 1107 in a 2×2 array, i.e. a 2×2integrated lens element placed on a sensor.

FIG. 14B illustrates a top view of the integrated 2×2 array shown inFIG. 14A.

The present invention is not restricted to a 2×2 array construction. AnyN×M configuration of lenses can be used as well according to principlesdescribed herein.

FIGS. 15A, 16A, and 17A, 18, 19 illustrate a construction of differentsizes of the lenses 1106 in a lens array.

FIGS. 15B, 16B, and 17B illustrate the sensors 1101 to be used inconnection with the lenses shown in FIGS. 15A, 16A, and 17A,respectively.

FIG. 20 illustrates another embodiment of a section of multi aperturedigital camera, i.e. a lens package 1200. Individual arrays 1201, 1202comprising lens elements are positioned within a housing 1203, andspacers 1204, 1205, 1206, 1207 are located on the sensor cover 1208mounted on sensor 1209. The bonding between the spacers 1204, 1205,1206, 1207 and the sensor cover 1208 is through an adhesive. An adhesiveis also present between the spacers 1204, 1205, 1206, 1207 and therespective arrays 1201, 1202.

FIG. 21 illustrates another embodiment of a section of multi aperturedigital camera, i.e. a lens package 1300. Individual arrays 1301, 1302comprising lens elements are positioned within a housing 1303, andspacers 1304, 1305, 1306 are located on the sensor cover 1307 beingmounted on sensor 1308. The bonding between the spacers 1304, 1305, 1306and the sensor cover 1307 is through an adhesive. An adhesive is alsopresent between the spacers 1304, 1305, 1306 and the arrays 1301, 1302.The polymer based lens elements are provided on transparant substrates1309, 1310 via replication technology. Examples of transparantsubstrates are glass, polymers, quartz, ceramics, sapphire, crystallinealumina, Yttria, yttrium aluminium garnet (YAG). The lens package 1300also includes light-shielding walls for preventing crosstalk betweenlight beams passing through adjacent lens elements of the lens array1301, 1302. The replicated lenses may be provided with one ore moreadditional layers, such as color filters, diaphragms, infra redreflecting layers, and anti reflection layers (not shown). Theseadditional layers can be present between the substrates 1309, 1310 andthe lens element replicated thereon. The lens elements of the lens array1301, 1302 can have different shapes, thicknesses, air spacethicknesses, polymer materials and aperture dimensions.

FIG. 22 illustrates another embodiment of a section of multi aperturedigital camera, i.e. a lens package 1400. Array 1401 comprising lenselements is positioned within a housing 1402, and spacers 1403, 1404,1405 are located on the sensor cover 1406 being mounted on sensor 1407.The bonding between the spacers 1403, 1404, 1405 and the sensor cover1406 is through an adhesive. An adhesive is also present between thespacers 1403, 1404, 1405 and the array 1401.

FIG. 23 illustrates another embodiment of a section of multi aperturedigital camera, i.e. a lens package 1500. Array 1501 comprising lenselements is positioned within a housing 1502, and spacers 1503, 1504,1505 are located on the sensor cover 1506 being mounted on sensor 1507.The bonding between the spacers 1503, 1504, 1505 and the sensor cover1506 is through an adhesive. An adhesive is also present between thespacers 1503, 1504, 1505 and the array 1501. The polymer based lenselements are provided on transparant substrates 1508, 1509 viareplication technology. Examples of transparant substrates are glass,polymers, quartz, ceramics, sapphire, crystalline alumina, Yttria,yttrium aluminium garnet (YAG).

The replica layer used in the present system can be composed of a UVcurable polymer, selected from the group of polycarbonates,polystyrenes, poly(meth)acrylates, polyurethanes, polyamids, polyimide,polyethers, polyepoxides and polyesters. A replica layer is obtained byusing a replication method in which use is made of a mould having aprecisely defined surface, for example an aspherical surface, wherein asmall amount of a radiation-curable resin, for example a UV curableresin, is applied to the mould surface. Subsequently, the resin isspread over the mould surface, so that the cavities present in the mouldare filled with the resin, whereupon the whole is subsequentlyirradiated for curing the resin and the thus cured product is removedfrom the mould. The cured product is a negative of the mould surface. Anadvantage of the replication process is that lenses having an intricaterefractive surface, such as an aspherical surface, can be produced insimple manner, without complicated processes of grinding and polishingthe lens body being required. In addition to that, the replica layer isdurably joined to the surface to which the replica layer is applied,without adhesives being used. In addition, there is no occurrence ofso-called “air gaps”, which lead to large refractive index transitionsbetween the surface and the air layer that is present.

Suitable UV curable compositions are: polycarbonates, includingdiethylene glycolbis-(allyl)carbonate, polystyrenes, includingpolychlorine styrene, polyacrylates, such as poly(trifluoroethylmethacrylate), poly(isobutyl methacrylate), poly(methylacrylate),poly(methyl methacrylate), poly(alphamethyl bromium acrylate),poly(methacrylic acid)-2,3-dibromium propylpoly(phenyl methacrylatepoly(pentachlorine phenyl-methacrylate polymer), polyester compoundssuch as diallylphthalate, poly(vinyl-benzoate), poly(vinylnaphthalene),poly(vinylcarbazole) and silicones in the form of various types of resinmaterials, as well as acrylic resin, urethane resin, epoxy resin,enthiol resin or thiourethane resin or photopolymer.

Exposure preferably takes place with an intensity of between 100 en 2000W/cm<2>, in particular 700 W/cm<2>, and a dose of 1-15 J/cm<2>, inparticular 7 J/cm<2>, a wavelength in the 320-400 nm range and anexposure time of 1-60 seconds, in particular 10 seconds.

Suitable UV curable adhesive compositions include GAFGARD233 (marketedby DuPont, type vinylpyrrolidone), Norland Inc. NOA-61, NOA-63, NOA-65,Three bond AVR-100 and Sony Chemical UV-1003, possibly provided with theusual additives such as initiators, reactive or nonreactive dilutants,crosslinking agents, fillers, pigments and anti-shrinkage agents.

Spacers mentioned in the Figs. are made of a rigid material, for exampleglass, silicon or a composite material such as FR4. In an embodiment thespacer plate is so configured that it will not interfere with the lightpath through the two separate lens elements, The spacer plate comprisesan opening which is positioned coaxially with a main optical axis of thelens element in question, whilst in a special embodiment the side ofsaid opening is provided with an anti-reflective coating.

The color filters, Infrared blocking filters, apertures andantireflection coatings on the substrates or lens surfaces can bemanufactured according to well known industrial processes, like coatingprocesses chemical vapor deposition, physical vapor deposition.

Suitable technologies regarding a multi-aperture camera throughassembling discrete optical elements, lens housing and optical blockingstructures are disclosed in U.S. Patent Publication Nos. 2010/0127157and US2010/0039713. These documents are incorporated by referenceherein. The optical elements can be manufactured through injectionmolding, glass molding of a thermoplast, or by pressing a glass preshapein a single cavity or plural cavity mold.

Suitable technologies for manufacturing coverplates lens holders forwafer level optics camera are disclosed in U.S. Patent Publication Nos.2010/0052192, 2009/0321861, and 2010/0117176, which are incorporated byreference herein.

Additional Configurations Considerations

Throughout this specification, some embodiments have used the expression“coupled” along with its derivatives. The term “coupled” as used hereinis not necessarily limited to two or more elements being in directphysical or electrical contact. Rather, the term “coupled” may alsoencompass two or more elements are not in direct contact with eachother, but yet still co-operate or interact with each other, or arestructured to provide a thermal conduction path between the elements.

Likewise, as used herein, the terms “comprises,” “comprising,”“includes,” “including,” “has,” “having” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus.

In addition, use of the “a” or “an” are employed to describe elementsand components of the embodiments herein. This is done merely forconvenience and to give a general sense of the invention. Thisdescription should be read to include one or at least one and thesingular also includes the plural unless it is obvious that it is meantotherwise.

Finally, as used herein any reference to “one embodiment” or “anembodiment” means that a particular element, feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. The appearances of the phrase “in oneembodiment” in various places in the specification are not necessarilyall referring to the same embodiment.

Upon reading this disclosure, those of skill in the art will appreciatestill additional alternative structural and functional designs from theprinciples herein. Thus, while particular embodiments and applicationshave been illustrated and described, it is to be understood that thedisclosed embodiments are not limited to the precise construction andcomponents disclosed herein. Various modifications, changes andvariations, which will be apparent to those skilled in the art, may bemade in the arrangement, operation and details of the method andapparatus disclosed herein without departing from the spirit and scopedefined in the appended claims.

The invention claimed is:
 1. A multi-lens camera system, comprising: afirst lens configured to direct light collected from a field of viewonto a first image sensor portion, the collected light comprising lightfrom a first portion of the field of view that is geometricallydistorted according to a first geometric distortion function; a secondlens configured to direct light collected from the field of view onto asecond image sensor portion, the collected light comprising light from asecond portion of the field of view that is geometrically distortedaccording to second geometric distortion function; and an image sensorcomprising the first image sensor portion and the second image sensorportion and configured to capture light incident upon the first imagesensor portion and the second information sensor portion to form animage, the image sensor further configured to combine luminanceinformation from the geometrically distorted light from the firstportion of the field of view and luminance information from thegeometrically distorted light from the second portion of the field ofview to form combined luminance information for the image.
 2. Themulti-lens camera system of claim 1, wherein the first geometricdistortion function is different than the second geometric distortionfunction.
 3. The multi-lens camera system of claim 1, wherein thegeometrically distorted light comprises magnified collected light. 4.The multi-lens camera system of claim 1, wherein each lens geometricallydistorts collected light responsive to the optical properties of thelens.
 5. The multi-lens camera system of claim 4, wherein the opticalproperties of each lens comprise one of: the shape of the lens, thethickness of the lens, the air space thickness of the lens, the lensmaterials, and the aperture dimensions of the lens.
 6. The multi-lenscamera system of claim 1, wherein at least one of the lenses includes aneutral density filter.
 7. The multi-lens camera system of claim 1,wherein at least one of the lenses includes a chromatic filter.
 8. Themulti-lens camera system of claim 1, wherein at least one of the lensesincludes a polarizing filter.
 9. A method for improving imageresolution, comprising: receiving, from a first lens configured todirect light collected from a field of view onto a first image sensorportion, collected light comprising geometrically distorted light from afirst portion of the field of view; receiving, from a second lensconfigured to direct light collected from the field of view onto asecond image sensor portion, collected light comprising geometricallydistorted light from a second portion of the field of view; capturingthe received light; and generating image luminance information based onthe captured geometrically distorted light from the first portion of thefield of view and the captured geometrically distorted light from thesecond portion of the field of view.
 10. The method of claim 9, furthercomprising: correcting the geometrically distorted light; generatingimage chrominance information based on the corrected geometricallydistorted light; and generating the image based on the image luminanceinformation and the image chrominance information.
 11. The method ofclaim 10, wherein the geometrically distorted light is upscaled beforeit is corrected.
 12. The method of claim 9, wherein each lens distortslight according to a geometric distortion, the geometric distortioncomprising a function of field of view location.
 13. The method of claim9, wherein the geometrically distorted light comprises magnifiedcollected light.
 14. The method of claim 9, wherein each lensgeometrically distorts collected light responsive to the opticalproperties of the lens.
 15. The method of claim 14, wherein the opticalproperties of each lens comprise one of: the shape of the lens, thethickness of the lens, the air space thickness of the lens, the lensmaterials, and the aperture dimensions of the lens.
 16. The method ofclaim 9, wherein at least one of the lenses includes a neutral densityfilter.
 17. The method of claim 9, wherein at least one of the lensesincludes a chromatic filter.
 18. The method of claim 9, wherein at leastone of the lenses includes a polarizing filter.